Method and apparatus for charging batteries at reduced overcharge levels

Abstract

Battery charging methods and associated chargers which are capable of rapidly charging a battery while subjecting it to reduced levels of overcharging. The methods described are capable of being utilized within numerous battery charging systems for batteries spanning a range of chemistries, such as lead-acid, nickel-based, and lithium-based batteries. Upon detection of the onset-of-overcharge during the charge process, a variable voltage lid is imposed (V LID =ν(φ)+βlogφ+κφ) which reduces the maximum voltage that may be applied to the battery as a function of charge acceptance which is typically estimated by a calculation based on state-of-charge. Additionally, the voltage lid can be approximated with step-wise voltage lids which are responsive to the level of charge acceptance within the battery.

What is claimed is:  
     
       1. A method of charging a battery, comprising: 
       (a) applying a controlled level of current to the battery; and  
       (b) modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.  
     
     
       2. A method of charging a battery, comprising: 
       (a) supplying a charging current to a battery;  
       (b) detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       (c) decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited.  
     
     
       3. A method as recited in  claim 2 , further comprising supplying charge current to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged. 
     
     
       4. A method as recited in  claim 2 , further comprising supplying the charge current to the battery at a constant rate and limiting the charger current by a maximum voltage lid. 
     
     
       5. A method as recited in  claim 2 , further comprising providing a stepwise current output that controlled according to the voltage lid. 
     
     
       6. A method as recited in  claim 2 , further comprising detecting the onset-of-overcharge at a predetermined level of SOC in relation to the applied current. 
     
     
       7. A method as recited in  claim 6 , further comprising empirically determining a relationship between the onset-of-overcharge and the SOC as a function of applied current and temperature. 
     
     
       8. A method as recited in  claim 2 , further comprising detecting the level of outgassing of the battery and determining the onset-of-overcharge by the level of detected outgassing. 
     
     
       9. A method as recited in  claim 2 , wherein the voltage lid is a function of battery state-of-charge given by V LID =ν(φ)+βlogφ+κφ. 
     
     
       10. A method as recited in  claim 9 , further comprising approximating the voltage lid by a series of discrete steps having a step size determined by the degree of matching required by the level of overcharging to be allowed within a particular application. 
     
     
       11. A method as recited in  claim 10 , further comprising providing at least three steps in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge. 
     
     
       12. A method as recited in  claim 2 , further comprising approximating the voltage lid by functions representing similar response profiles which decrease as the state-of-charge progresses, and determining a degree of function matching by the level of overcharging to be allowed within a particular application. 
     
     
       13. A method as recited in  claim 2 , further comprising determining the voltage lid by reaching a normalized maximum gassing rate attained during charging of the battery. 
     
     
       14. A method as recited in  claim 13 , further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging. 
     
     
       15. A method as recited in  claim 2 , further comprising determining the voltage lid by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery. 
     
     
       16. A method as recited in  claim 2 , further comprising charging a battery selected from the group of batteries consisting of lead-acid, nickel-cadmium, nickel-metal-hydride, lithium-ion, nickel-based, and lithium-based. 
     
     
       17. A method as recited in  claim 2 , further comprising applying a high battery charging rate exceeding 1.2C to a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly. 
     
     
       18. A method of charging a battery, comprising the steps of: 
       (a) applying charging current to the battery at a controlled level limited by a voltage lid;  
       (b) detecting an onset-of-overcharge condition while charging at the existing level of charge current;  
       (c) reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and  
       (d) repeating steps (b) and (c) until the applied current to the battery has been limited to a sufficiently low level to constitute a desired “float charge”.  
     
     
       19. A method as recited in  claim 18 , further comprising estimating the onset-of-overcharge condition detection according to the conditions of SOC, applied current and temperature. 
     
     
       20. A method as recited in  claim 18 , further comprising detecting outgassing of the battery and determining the onset-of-overcharge condition by the level of detected outgassing which occurs. 
     
     
       21. A method as recited in  claim 18 , further comprising providing a stepwise current output that is controlled according to the voltage lid. 
     
     
       22. An apparatus for charging a battery, comprising: 
       (a) means for applying a controlled level of current to the battery; and  
       (b) means for modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.  
     
     
       23. An apparatus for charging a battery, comprising: 
       (a) means for supplying a charging current to a battery;  
       (b) means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       (c) means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.  
     
     
       24. An apparatus as recited in  claim 23 , wherein the charge current is supplied to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the voltage source and the battery being charged. 
     
     
       25. An apparatus as recited in  claim 23 , wherein the charge current is supplied to the battery at a constant rate and is limited by a maximum voltage lid. 
     
     
       26. An apparatus as recited in  claim 23 , further comprising means for providing stepwise current output controlled according to the voltage lid. 
     
     
       27. An apparatus as recited in  claim 23 , wherein the onset-of-overcharge is detected at a predetermined level of SOC in relation to the applied current. 
     
     
       28. An apparatus as recited in  claim 27 , wherein an empirical relationship between the onset-of-overcharge and the SOC is empirically determined in relation to parameters comprising applied current and temperature. 
     
     
       29. An apparatus as recited in  claim 23 , further comprising means for detecting outgassing of the battery and wherein the onset-of-overcharge is determined by the level of detected outgassing. 
     
     
       30. An apparatus as recited in  claim 23 , wherein the voltage lid is a function of battery state-of-charge given by V LID =ν(φ)+βlogφ+κφ. 
     
     
       31. An apparatus as recited in  claim 30 , wherein the voltage lid is approximated by a series of discrete steps having a step size determined by a degree of matching required by the level of overcharging to be allowed within a particular application. 
     
     
       32. An apparatus as recited in  claim 31 , wherein at least three steps are provided in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge. 
     
     
       33. An apparatus as recited in  claim 23 , wherein the voltage lid is approximated by functions representing similar response profiles which decrease as the state-of-charge progresses, with a degree of function matching being determined by the level of overcharging to be allowed within a particular application. 
     
     
       34. An apparatus as recited in  claim 23 , wherein the voltage lid is determined by reaching a normalized maximum gassing rate attained during charging of the battery. 
     
     
       35. An apparatus as recited in  claim 34 , wherein the normalized maximum gassing rate is set to approximately 1.0 SCCM/A during charging. 
     
     
       36. An apparatus as recited in  claim 23 , wherein the voltage lid is determined by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery. 
     
     
       37. An apparatus as recited in  claim 23 , wherein the battery charges is selected from the group of batteries consisting of lead-acid, nickel-cadmium, nickel-metal-hydride, lithium-ion, nickel-based, and lithium-based. 
     
     
       38. An apparatus as recited in  claim 23 , wherein said apparatus is configured for a high battery charging rate exceeding 1.2C for a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly. 
     
     
       39. An apparatus for charging a battery, comprising: 
       (a) means for applying charging current to the battery at a controlled level limited by a voltage lid;  
       (b) means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;  
       (c) means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and  
       (d) means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “float charge”.  
     
     
       40. An apparatus as recited in  claim 39 , wherein the onset-of-overcharge condition detection is estimated according to the conditions of SOC, applied current and temperature. 
     
     
       41. An apparatus as recited in  claim 39 , further comprising means for detecting outgassing of the battery, and wherein the onset-of-overcharge condition is determined by the level of detected outgassing which occurs. 
     
     
       42. An apparatus as recited in  claim 39 , further comprising means for providing stepwise current output controlled according to the voltage lid. 
     
     
       43. A method of charging a battery, comprising: 
       supplying a charging current to a battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited.  
     
     
       44. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       wherein charge current is supplied to the battery at a constant rate which is limited by a maximum set by said voltage lid.  
     
     
       45. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       wherein a stepwise current output is provided which is controlled according to said voltage lid.  
     
     
       46. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       detecting the level of outgassing of the battery and determining the onset-of-overcharge by the level of detected outgassing.  
     
     
       47. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       wherein said voltage lid is a function of battery state-of-charge given by V LID =νφ+βlogφ+κφ.  
     
     
       48. A method as recited in  claim 47 , further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging. 
     
     
       49. A method as recited in  claim 48 , further comprising providing at least three steps in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge. 
     
     
       50. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       approximating the voltage lid by functions representing similar response profiles which decrease as the state-of-charge progresses, and determining a degree of function matching by the level of overcharging to be allowed within a particular application.  
     
     
       51. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       determining said voltage lid by reaching a normalized maximum gassing rate attained during charging of the battery.  
     
     
       52. A method as recited in  claim 51 , further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging. 
     
     
       53. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       determining said voltage lid by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery.  
     
     
       54. A method of charging a battery, comprising: 
       supplying a charging current to a battery;  
       detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and  
       wherein said charging current is supplied as a high charging rate exceeding 1.2C to said battery when its state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.  
     
     
       55. A method of charging a battery, comprising the steps of: 
       applying a stepwise charging current output to the battery at a controlled level limited according to a voltage lid;  
       detecting an onset-of-overcharge condition while charging at the existing level of charge current;  
       reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and  
       repeating the above two steps until the applied current to the battery has been limited to a sufficiently low level to constitute a desired “float charge”.  
     
     
       56. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery from a controllable current source that forces current through a series resistance, said series resistance comprising the voltage source and the battery being charged;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.  
     
     
       57. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery at a constant rate which is limited by a maximum voltage lid;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.  
     
     
       58. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery as a stepwise current output controlled according to the voltage lid;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.  
     
     
       59. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current;  
       means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected; and  
       means for detecting outgassing of the battery and wherein the onset-of-overcharge is determined by the level of detected outgassing.  
     
     
       60. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition;  
       wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.  
       wherein the voltage lid is a function of battery state-of-charge given by V LID =νφ+βlogφ+κφ.  
     
     
       61. An apparatus as recited in  claim 60 , wherein said voltage lid is approximated by a series of discrete steps having a step size determined by a degree of matching required by the level of overcharging to be allowed within a particular application. 
     
     
       62. An apparatus as recited in  claim 61 , wherein at least three steps are provided in which maximum fixed voltages are applied to said battery charging, the three steps being defined within an associated three ranges of state-of-charge. 
     
     
       63. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;  
       wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;  
       wherein said voltage lid is approximated by functions representing similar response profiles which decrease as the state-of-charge progresses, with a degree of function matching being determined by the level of overcharging to be allowed within a particular application.  
     
     
       64. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;  
       wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;  
       wherein the voltage lid is determined by reaching a normalized maximum gassing rate attained during charging of the battery.  
     
     
       65. An apparatus as recited in  claim 64 , wherein said normalized maximum gassing rate is set to approximately 1.0 SCCM/A during charging. 
     
     
       66. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;  
       wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;  
       wherein said voltage lid is determined by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during said charging of the battery.  
     
     
       67. An apparatus for charging a battery, comprising: 
       means for supplying a charging current to a battery;  
       means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and  
       means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;  
       wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;  
       wherein said apparatus is configured for a high battery charging rate exceeding 1.2C for a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.  
     
     
       68. An apparatus for charging a battery, comprising: 
       means for applying charging current to the battery at a controlled level limited by a voltage lid;  
       means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;  
       means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential;  
       means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “float charge”; and  
       means for detecting outgassing of said battery, and wherein the onset-of-overcharge condition is determined by the level of detected outgassing which occurs.  
     
     
       69. An apparatus for charging a battery, comprising: 
       means for applying charging current to the battery at a controlled level limited by a voltage lid;  
       means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;  
       means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential;  
       means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “float charge”; and  
       wherein said charging current is applied stepwise and controlled according to said voltage lid.  
     
     
       70. A method of charging a battery, comprising: 
       applying a controlled level of charge current to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged; and  
       modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.  
     
     
       71. An apparatus for charging a battery, comprising: 
       means for applying a controlled level of current to the battery;  
       wherein said controlled level of current is applied through a series resistance, said series resistance comprising the voltage source and the battery being charged; and  
       means for modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.